Delete README.md

Python_files/ex4/README.md

-This file Contains the Cora and Citeseer datasets [1] for node classification and the Facebook [2] and PPI [3] datasets for link prediction.
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-References:
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-[1] Sen, Prithviraj, et al. "Collective classification in network data." AI magazine 29.3 (2008): 93-93.
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-[2] J. Leskovec and A. Krevl. SNAP Datasets: Stanford largenetwork dataset collection. http://snap.stanford.edu/data,June 2014.
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-[3] Breitkreutz, Bobby-Joe, et al. "The BioGRID interaction database: 2008 update." Nucleic acids research 36.suppl_1 (2007): D637-D640.